The present invention relates to an ophthalmic lens made of organic glass with an impact-resistant interlayer and to a process for its manufacture.
Ophthalmic lenses made of organic glass are more sensitive to scratching and to abrasion than those made of inorganic glass.
It is known to protect surface of this type of lens with hard coatings, generally of the polysiloxane type.
It is also known to treat lenses made of organic glass so as to prevent the formation of interfering reflections which are troublesome for the wearer of the lens and his or her interlocutors. The lens then comprises a single- or multilayer anti-reflective coating made of inorganic material.
When the lens comprises an abrasion-resistant coating in its structure, the anti-reflective coating is deposited onto the surface of the abrasion-resistant layer. Such layering reduces the impact strength by stiffening the system, which becomes breakable. This problem is well known in the industry of ophthalmic lenses made of organic glass.
A number of solutions have been proposed in the state of the art. They generally consist in applying an impact-resistant primer to the substrate of the lens and then applying the hard abrasion-resistant coating and, lastly, the anti-reflective coating.
Japanese Patents 63-141001 and 63-87223 describe plastic lenses comprising an impact-resistant primer based on thermoplastic polyurethane resin. U.S. Pat. No. 5,015,523 recommends acrylic impact-resistant primers and Application EP-040411 describes impact-resistant primers based on heat-curable polyurethane.
The processes of the prior art defined above have the disadvantages of employing impact-resistant primers which are thick and of being ill-adapted to the problems of use of these coatings on industrial scale.
In the actual industrial manufacture of ophthalmic lenses made of organic glass the glasses are generally coated with a hard abrasion-resistant layer, but the anti-reflective treatment is not systematic and is performed, to order, on stock glasses in a limited number.
Processes for the manufacture of the abrasion-resistant and anti-reflective lenses of the prior art employ a collection of stock glasses comprising not only a hard abrasion-resistant coating but also an impact-resistant primer, whereas only a proportion of these glasses has to be given an anti-reflective treatment.
A consequence of these techniques is a multiplicity of sometimes pointless operations, with the concomitant oncosts of production of the final glass.
On the industrial scale it would be desirable to search for a process for the manufacture of abrasion-resistant and anti-reflective ophthalmic lenses making it possible to employ, when required, stock glasses coated only with an abrasion-resistant layer for subsequent treatment with an anti-reflective coating.